Glycogen cycle enzymes and other enzymes regulated by hormonally-controlled phosphorylations are being isolated and characterized. Particular attention is directed toward defining the regulatory roles of phosphoprotein phosphatases. Factors controlling the developmental appearance of these enzymes are being studied in fetal liver explants in culture. Neonatal liver glucose homeostasis is being studied using an isolated perfused monkey liver system. Evidence that galactose plays a unique role in regulating neonatal liver glucose homeostasis is being examined in this system.